1. Field
The present disclosure relates to a dielectric paste composition, method of forming a dielectric layer, a dielectric layer, and a device including the dielectric layer.
2. Description of the Related Art
High-K dielectric layers are widely used as interlayer dielectric layers of film condensers or capacitors. Such devices may be used in electrical devices, including communication devices, power supplies, and inverters, for example. Also, high-K dielectric layers may be used in piezoelectric elements, for pyroelectric elements, and may be used to support a transfer body. For example, a high-K dielectric layer of a powder electroluminescent (“EL”) device or a thick dielectric electroluminescent (“TDEL”) device may be disposed adjacent to an emission layer in a display device, thereby contributing to an increase in brightness of the emission layer.
A high-K dielectric layer may be formed by melt-kneading or coating, both of which are known to one skilled in the art and can be performed without undue experimentation.
The melt-kneading method includes kneading a polymer and inorganic dielectric particles together at a temperature higher than a melting point of the polymer, and the resulting mixture is formed as a film by melt-extrusion or film blowing (e.g., blown film extrusion). Melt-kneading is disclosed in Japanese Patent Laid-Open Publication Nos. 2000-501549 and 2000-294447, the contents of which in their entirety are herein incorporated by reference. However, it is difficult to form a thin film dielectric layer with a small number of pores using the melt-kneading method.
The coating method includes coating or printing a dielectric paste composition including high-k inorganic dielectric particles, a binder, and a solvent on a substrate to form a dielectric layer. When a dielectric layer is prepared by the coating method, a dielectric constant of the dielectric layer may be increased by increasing a content of the inorganic dielectric particle in the dielectric paste composition. However, when a concentration of the inorganic dielectric particles in the dielectric paste composition is excessively high, the viscosity of the dielectric paste composition is increased, and thus it is difficult to suitably apply the composition using a printing or coating process. Also, a dielectric layer formed using a dielectric paste composition having a high concentration of inorganic dielectric particles is undesirably thick. To address these and other problems, use of at least two kinds of inorganic dielectric particles having different sizes to increase a dielectric constant by increasing a packing factor, or use of a solvent having a boiling point of 160° C. or higher to prevent loss of a dielectric constant by preventing pore formation, have been proposed. See, for example, Korean Patent Publication No. 2006-0002844, the content of which in its entirety is herein incorporated by reference. In addition, to improve the dispersion and coating properties of the inorganic dielectric particle in a dielectric paste composition, an additive, such as a dispersant, an antifoaming agent, a leveling agent, and/or an antioxidant are used. See, for example, Korean Patent Publication No. 2005-0049789, the content of which in its entirety is herein incorporated by reference. Moreover, to form a dielectric layer with excellent surface properties, a leveling agent, a plasticizer, and/or an adhesive is used. See, for example, Korean Patent No. 0718923, the content of which in its entirety is herein incorporated by reference. Also, the inorganic dielectric particle may be surface-treated, or a dispersant, a surfactant, and/or a coupling agent may be added. See, for example, Korean Patent Publication No. 2008-0041711, the content of which in its entirety is herein incorporated by reference. However, when a dielectric layer is formed using a commercially available coating method such as the foregoing, the dielectric constant of the dielectric layer is indirectly increased by using additives, which provide an improvement in dispersibility, coating properties, and surface smoothness of the dielectric paste composition to indirectly improve the dielectric constant of the dielectric layer formed using the dielectric paste composition, and thus there is a limit to the extent to which the dielectric constant may be improved using such methods. Thus there remains a need for an improved composition for forming a dielectric layer.